Long-Term Outcomes of an International Cooperative Study of Intraoperative Radiotherapy Upfront Boost With Low Energy X-Rays in Breast Cancer

Purpose

The purpose of this study was to assess the effectivity of upfront kilovoltage intraoperative radiotherapy (IORT) as a boost in high-risk early-stage breast cancer patients from an international pooled cohort.

Materials/Methods

Patients from four centers in three different countries were retrospectively screened. Those with a minimum 1-year follow-up were included. Cumulative local (LR), regional (RR), and distant metastasis rates (DM) were analyzed. Additionally, the estimated overall survival (OS) was assessed. The Cox regression analysis was performed to identify failure predicting factors.

Results

A total of 653 patients from centers in Peru, Spain, and Germany were included. The median follow-up was 55 (12–180) months, and age was 58 (27–86) years. Clinical tumor (T) staging was T1 65.85%, T2 30.17%, and T3 3.98%. Positive margins were found in 7.9% and in-situ component in 20.06%. The median IORT dose was 20 (6–20). The median time from IORT to EBRT was 74.5 (13-364) days. An overall 3.4% (n = 22) of patients developed local recurrence at some point during follow-up. The 12-, 60-, and 120-month cumulative LR were 0.3%, 2.3%, and 7.9%, respectively. After multivariate analysis, only age <50 remained to be a significant prognostic factor for local recurrence (HR 0.19, 95% CI 0.08–0.47; p < 0.05). The 10-year estimated OS was 81.2%.

Conclusion

Upfront boost with IORT yields similar local control outcomes to those EBRT-based reports. Results from prospective trials, regarding toxicity, cosmesis, and effectivity are awaited to confirm these findings.

Detection of setup errors with a body-surface laser-scanning system for whole-breast irradiation after breast-conserving surgery

PURPOSE

We compared the setup errors determined by an optical imaging system (OSIS) in women who received breast-conserving surgery (BCS) followed by whole-breast radiotherapy (WBRT) with those from cone-beam computed tomography (CBCT) carried out routinely.

METHODS

We compared 130 setup errors in 10 patients undergoing WBRT following BCS by analyzing the translational and rotational couch shifts via CBCT and OSIS. Patients were treated with intensity-modulated radiotherapy (IMRT). The patient outline extracted from the planning reference Computed tomography (CT) was used as the reference for OSIS and CBCT alignment during treatment. We detected the setup uncertainty using CBCT and OSIS at the first five fractionations of RT and then twice a week.

RESULTS

The absolute translational setup error (mean ± Standard deviation (SD)) in x (lateral), y (longitudinal), and z (vertical) axes detected by the OSIS was 0.14 ± 0.18, 0.15 ± 0.14, and 0.13 ± 0.13 cm, respectively. The rotational setup error (mean ± SD) in Rx (pitch), Ry (roll), and Rz (yaw) axes was 0.77 ± 0.54, 0.76 ± 0.61, and 1.23 ± 0.95, respectively. Significant difference is observed only in one direction (Rx, p = 0.03) in the paired setup errors obtaining from OSIS and CBCT, without significant differences in five directions.

CONCLUSION

OSIS is a repeatable and reliable system that can be used to detect misalignments with accuracy, which is capable of supplementing CBCT for WBRT after BCS. We believe that an OSIS may be easier to use, quicker, and reduce overall dose as this method of patient alignment does not require ionizing radiation.

A study of the dosimetric impact of daily setup variations measured with cone-beam CT on three-dimensional conformal radiotherapy for early-stage breast cancer delivered in the prone position

PURPOSE

To evaluate the dosimetric impact of daily positioning variations measured with cone-beam computed tomography (CBCT) on whole-breast radiotherapy patients treated in the prone position.

METHODS

Daily CBCT was prospectively acquired for 30 consecutive patients positioned prone. Treatment for early-stage (≤II) breast cancer was prescribed with standard dose (50 Gy/25 fractions) or hypofractionation (42.56 Gy/16 fractions) for 13 and 17 patients, respectively. Systematic and random errors were calculated from the translational CBCT shifts and used to determine population-based setup margins. Mean translations (±one standard deviation) for each patient were used to simulate the dosimetric impact on targets (PTV_eval and lumpectomy cavity), heart, and lung. Paired Student's t tests at α = 0.01 were used to compare dose metrics after correction for multiple testing (P < 0.002). Significant correlation coefficients were used to identify associations (P < 0.01).

RESULTS

Of 597 total fractions, 20 ± 13% required patient rotation. Mean translations were 0.29 ± 0.27 cm, 0.41 ± 0.34 cm, and 0.48 ± 0.33 cm in the anterior-posterior, superior-inferior, and lateral directions leading to calculated setup margins of 0.63, 0.88, and 1.10 cm, respectively. Average three-dimensional (3D) shifts correlated with the maximum distance of breast tissue from the sternum (r = 0.62) but not with body-mass index. Simulated shifts showed significant, but minor, changes in dose metrics for PTV_eval, lung, and heart. For left-sided treatments (n = 18), mean heart dose increased from 109 ± 75 cGy to 148 ± 115 cGy. Shifts from the original plan caused PTV_eval hotspots (V105%) to increase by 5.2% ± 3.8%, which correlated with the total MU of wedged fields (r = 0.59). No significant change in V95% to the cavity was found.

CONCLUSIONS

Large translational variations that occur when positioning prone breast patients had small but significant dosimetric effects on 3DCRT plans. Daily CBCT may still be necessary to correct for rotational variations that occur in 20% of treatments. To maintain planned dose metrics, unintended beam shifts toward the heart and the contribution of wedged fields should be minimized.

Incidence of organizing pneumonia after whole-breast radiotherapy for breast cancer, and risk factor analysis

Radiation-induced organizing pneumonia (OP) reportedly occurs in ~2% of patients who receive whole-breast radiotherapy (WBRT). Though there are several reported risk factors, they remain unclear and controversial. We analyzed the incidence of and risk factors for OP after WBRT at our institution. We analyzed 665 breast cancer patients (with WBRT of 679 breasts) who underwent WBRT from October 2007 to September 2012 at our institution and were followed up for more than 1 year after completion of WBRT. Factors included in the analysis were age, the side affected, central lung distance (CLD), radiation dose, concurrent endocrine therapy, and chemotherapy. The median age was 56 years (range, 23-89 years). The sides affected were left, right and bilateral in 342, 309 and 14 patients, respectively. The median CLD was 1.1 cm (range, 0-3.0 cm). Concurrent endocrine therapy was performed in 236 patients, and chemotherapy was given in 215 patients; of these, 4 received concurrent chemotherapy. OP developed in nine patients (1.4%). The median time taken to develop OP after the completion of WBRT was 4 months (range, 2-12 months). All nine patients were treated with steroids, and symptoms promptly improved, except in two patients who relapsed. Statistical analysis revealed that only CLD (≥1.5 cm) was significantly associated with the development of OP (P = 0.004). In conclusion, the incidence of OP after WBRT was 1.4%, and CLD was a significant risk factor. In these patients, OP was controlled with steroid administration.